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Int J Clin Exp Pathol 2011;4(1):22-31

Original Article
Absence of microsatellite instability in mucinous carcinomas of the breast

Magali Lacroix-Triki, Maryou B Lambros, Felipe C Geyer, Paula H Suarez, Jorge S Reis-Filho, Britta Weigelt

Molecular Pathology Team, The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, SW3 6JB, UK; Institut
Claudius Regaud, 31052 Toulouse, France, Cancer Research UK, London Research Institute, WC2A 3LY, UK

Received November 7, 2010; accepted November 5, 2010; Epub November, 2010; published January 1, 2011

Abstract: Microsatellite instability (MSI) is a form of genetic instability that results from defects in DNA mismatch repair. MSI is reported to be
rare in unselected breast cancers, however it is a common feature in subsets of colorectal, ovarian and endometrial cancers. In these
anatomical sites, MSI-high carcinomas often display a mucinous histology. The aim of this study was determine whether mucinous
carcinomas of the breast would more frequently display MSI-high than invasive ductal carcinomas of no special type (IDC-NSTs). The
expression of four MSI markers (i.e. MSH2, MSH6, MLH1 and PMS2) was immunohistochemically assessed in 35 mucinous breast
carcinomas and 35 histological grade- and oestrogen receptor (ER) status-matched IDC-NSTs, and in a series of 245 invasive breast cancers.
Cases were considered as potentially MSI-high if tumour cells lacked expression of at least two MSI markers and internal controls displayed
nuclear staining. Nine mucinous carcinomas were microdissected and subjected to MSI analysis by PCR using the MSI markers BAT26 and
BAT40. No immunohistochemical evidence of MSI-high was found in the 35 mucinous carcinomas and 35 grade- and ER-matched IDC-NSTs,
and in the cohort of 245 invasive breast cancers. In addition, no evidence of MSI-high was observed by PCR analysis using the BAT26 and
BAT40 markers in the nine mucinous carcinomas tested. Our results demonstrate that MSI-high phenotype is remarkably rare in invasive
breast cancer, and that, in contrast to mucinous carcinomas of other anatomical sites, MSI is not a common event in mucinous carcinomas of
the breast. (IJCEP1011001).

Keywords: Mucinous carcinoma, breast cancer, mismatch repair, microsatellite instability, immunohistochemistry, genetics

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Address all correspondence to:
Britta Weigelt, PhD
Cancer Research UK, London Research Institute
44 Lincoln’s Inn Fields
London, WC2A 3LY, UK.
Tel: +44 72693622, Fax: +44 2072693094